The present invention relates to smart igniter detonators in general and to systems for communicating with smart igniter detonators in particular.
A critical factor in the safe use of explosives and pyrotechnic devices is to make the explosive material or gas generating material relatively insensitive to environmental factors which might initiate an explosion or deflagration. This is normally accomplished by a combination of packaging and choice of reactive materials. The insensitivity of the reactive materials making up the gas generator or the explosive should ideally be extended to the initiation charge as well as the primary charge. This has resulted in the development of initiators in which a nonexplosive material is caused to explode by electrical means. The result is an explosive or gas generator charge that is relatively insensitive to shock, temperature, and even electromagnetic interference.
Classically a so-called hot-wire detonator initiates an explosive charge or gas generator by heating a wire in contact with the initiation charge. Such initiation requires an initiation charge that is relatively sensitive and requires the transmission of a substantial amount of current to the detonator.
Smart igniters are a class of devices which combine a nonthermal igniter, typically a semiconductor bridge igniter with a microprocessor, together with the necessary electrical components for accumulating and discharging an electrical charge to activate the igniter. The microprocessor allows the smart igniter to interface with a databus for transmitting status data, and for receiving a digitally encoded initiation/detonation signal, as explained more fully in U.S. Pat. No. 6,275,756, which is incorporated herein by reference. The advantages of the smart igniter are that: the status of each igniter may be continually monitored, multiple igniters may be electrically connected in parallel by a single pair of wires making up a data bus, and ignition is under computer control by sending a signal to the unique address that allows each smart igniter to be individually controlled.
Using smart igniters places individual igniters on what amounts to a data bus or network which is inevitably subject to the limitations of all data transmission, which is that of the signal transmitted over electrical lines becoming degraded. Where the electrical characteristics of wire transmission lengths exceed hundreds of feet or yards, the result is large values of electrical capacitance and inductance. It is well known that using transmission wire cables with large values of capacitance and inductance creates problems with analog and digital communications including data latency, signal amplitude and power loss, and loss of waveform data pulse shape and timing accuracy and integrity. To gain full advantage of the benefits available through the use of smart igniters, a system of data bus repeaters is needed for use where the transmission of data between smart igniters is degraded by the length of the transmission lines.
The smart igniter bus system of this invention comprises a controller, a repeater connected by a bus to the controller, and one or more smart igniters connected by the bus to the repeater so that the repeater is between the smart igniters and the controller. The repeater receives data transmitted on the bus by the controller and processes the signal sent by the controller, with onboard logic. Utilizing the onboard logic the repeaters may be preprogrammed to, or may be instructed by the controller, to rebroadcast control signals sent by the controller, to only rebroadcast selected signals, or to generate and transmit new command signals. The repeaters also transmit power downstream of the repeater, for use by subsequent repeaters and the smart igniters.
The repeater thus provides the functionality of receiving and correcting a signal degraded by transmission line properties, the ability to command a greater number of smart igniters by reusing bus addresses, and blocking transmission of signals which are unneeded by the smart igniters which follow the repeater. The repeater also provides functionality between the smart igniters and the controller by receiving signals transmitted from the start igniters and again performing one or more of the functions of: correcting a signal degraded by transmission line properties, adding additional addressing information to a transmitted signal, and preventing retransmission of information unnecessary to be received by the controller.
It is a feature of the present invention to provide a smart igniter system which can function with long data bus transmission lines.
It is another feature of the present invention to provide a smart igniter system which can reduce traffic on some bus segments without reducing functionality.
It is a further feature of the present invention to provide a smart igniter system which can increase the number of smart igniters which can be addressed on a single bus.
Further features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.